The invention relates generally to telecommunication networks and, more particularly, to a vocoder capable of performing conversions for decoding functions for messages conforming to various transmission standards.
Wireless communications is characterized by plural communication standards, each of which are used by certain components and/or segments of a wireless telecommunications to define the operating environment under which messages are transmitted with that component and/or segment. Time Division Multiple Access (or xe2x80x9cTDMAxe2x80x9d) is a technology standard used to separate multiple conversation transmissions by allocating a discrete amount of frequency bandwidth to each user. In a TDMA digital wireless telephone system, three time slots are allocated within each frequency channel. A user is assigned a specific time slot within a frequency channel for transmissions. During the assigned time slot, the cellular telephone send bursts of information, each consisting of a portion of an encoded voice message. These bursts of information, commonly referred to as data packets, are then reassembled by the receiving equipment into the original voice message. Similar to TDMA, Frequency Division Multiple Access (or xe2x80x9cFDMAxe2x80x9d) is a technology standard which also separates multiple transmissions over a finite frequency allocation. In a FDMA digital wireless telephone system, each user is allocated an exclusive frequency band within a transmission channel. When the user completes their transmission, the band is reused by assigning it to a next user. Code Division Multiple Access (or xe2x80x9cCDMAxe2x80x9d), on the other hand, is a spread spectrum technology standard. In a CDMA digital wireless telephone system, a voice message is divided into a collection of speech bits, each of which is assigned a code. The encoded speech bits are scrambled and then transmitted over the air. Receiving equipment reassembles the original voice message from the received collection of scrambled speech bits.
Further complicating the situation is that broadly defined technical standards such as TDMA and CDMA typically encompass a variety of protocols. For example, the TDMA technical standard encompasses, among others, the Enhanced Full Rate Coding (or xe2x80x9cEFRCxe2x80x9d) protocol and the Vector Sum Excited Linear Prediction Coding (or xe2x80x9cVSELPxe2x80x9d) protocol while the CDMA technical standard encompasses, among others, the Enhanced Variable Rate Coding (or xe2x80x9cEVRCxe2x80x9d) protocol and the Qualcomm Code Excited Linear Predication (or xe2x80x9cQCELPxe2x80x9d) protocol. Finally, a digital wireless telephone system may conform to the Global System for Mobile Communications (or xe2x80x9cGSMxe2x80x9d) technical standard, which uses a mixed TDMA and FDMA access method. Finally, wireless transmissions of data are often conducted asynchronously, for example, using Radio Link Protocol (or xe2x80x9cRLPxe2x80x9d).
Within a wireless communications system, messages transmitted over the airlink, for example, messages exchanged between a mobile terminal and a base station, are digitally encoded while messages transmitted elsewhere within the communications system, for example, messages exchanged between the base station and the mobile switching center (or xe2x80x9cMSCxe2x80x9d) are analog messages. Thus, the base station must be equipped for both digital-to-analog (or xe2x80x9cD/Axe2x80x9d) decoding and analog-to-digital (or xe2x80x9cA/Dxe2x80x9d) encoding operations. However, D/A and A/D operations are different for each access technology standard such as TDMA, CDMA, FDMA and GSM, as well as for the various protocols which fall within a particular access technology standard.
Thus, the base station controller and other components of digital wireless telephone systems have been faced with the problem of receiving messages which conform to various access technologies, each having distinct encoding and decoding operations. To handle messages of different access technologies, base station controllers have been provided with separate vocoder resources, one for each access technology to be handled thereby. For example, while a base station controller would have a local vocoder equipped with a single resource for handling encoding and decoding operations in one access technology, messages configured in accordance with other access technologies were often shunted elsewhere within the wireless telecommunications network for handling. For example, an interworking function (or xe2x80x9cIWFxe2x80x9d) coupled to the base station controller is often used to encode and/or decode facsimile data by converting received digital fax data into analog modem tones and converting received analog modem tones into digital fax data.
It is, therefore, the object of this invention to provide a base station controller equipped with a multiple technology vocoder.
In one embodiment, the present invention is a base station controller which includes a call control resource manager which controls exchanges of messages between mobile terminals and a MSC. Messages received by the call control resource manager are transferred to a multiple technology vocoder coupled thereto for D/A or A/D conversion. To perform conversions, the multiple technology vocoder includes a first resource module for performing D/A and A/D conversions for messages configured in accordance with a first technology, a second resource module for performing D/A and A/D conversions for messages configured in accordance with a second technology and a selection manager for selecting one of said first and second resource modules to perform D/A and A/D conversions on the messages received from said call resource manager. In one aspect, the selection manager selects a resource module in response to a first control signal issued by a vocoder controller. In another, a buffer manager regulates the transmission of messages from the call control resource manager to the selection manager in response to a second control signal issued by the vocoder controller. In still other aspects, the first technology is TDMA, the second technology is CDMA and the multiple technology vocoder is embodied within a DSP (digital signal processor).
In another embodiment, the present invention is directed to a base station controller which includes a call control resource manager for controlling exchanges of messages between a mobile terminal and a MSC and a vocoder having a first interface coupled to receive, from the call control resource manager, messages originating at the mobile terminal and destined for the MSC, a second interface coupled to receive, from the call control resource manager, messages originating at the MSC and destined for the mobile terminal, a first resource module, coupled to the first and second interfaces, for performing D/A and A/D conversions for messages configured in accordance with a first protocol, a second resource module, coupled to the first and second interfaces, for performing D/A and A/D conversions for messages configured in accordance with a second protocol and a vocoder controller, coupled to the call control resource manager and the first and second interfaces, for configuring the first and second interfaces to handle messages of a selected one of the first and second protocols in response to information received from the call control resource manager.
In one aspect of this embodiment of the invention, the first interface further includes a reconfigurable buffer and a buffer manager which reconfigures the buffer to accept messages formatted in a selected one of the first and second protocols each time the vocoder controller detects a change in protocol. In another, the second interface is similarly constructed. In still others, the vocoder may further include a first selection manager for selecting one of the first and second resource modules to perform D/A conversions on messages originating at the mobile terminal and destined for the MSC and a second selection manager for selecting one of the first and second resource modules to perform A/D conversions on messages originating at the MSC. Each of the selection managers provide a path to the selected one of the first and second resource modules. The first and second protocols may be comprised of two TDMA protocols, two CDMA protocols, one TDMA protocol and one CDMA protocol, one TDMA protocol and one radio link protocol or one CDMA protocol and one radio link protocol.
In still another embodiment, the present invention is of a telecommunication network which includes a mobile terminal, first and second base station controllers and a MSC. The first base station controller includes a vocoder for performing D/A and A/D conversions for messages configured in accordance with a first protocol while the second base station controller includes a vocoder for performing D/A and A/D conversions for messages configured in accordance with a second protocol but is incapable of performing D/A and A/D conversions for messages configured in accordance with the first protocol. When the mobile terminal is coupled to the first base station controller via a first airlink, messages being exchanged between the mobile terminal and the MSC via the first base station controller are converted by the vocoder residing at the first base station controller. When the mobile terminal is coupled to the second base station controller via a second airlink, messages being exchanged between the mobile terminal and the MSC via the second base station controller are shunted, by the second base station controller, to the first base station controller via a direct link therebetween for conversion by the vocoder residing at the first base station controller.